The main objective of the study was to better understand the causes of stereotypic behaviors in stalled pigs. A first experiment was conducted with gilts to evaluate behavioral and physiological responses of four genotypes (Meishan, Yorkshire, Meishan x Yorkshire, and Yorkshire x Meishan) to two types of gestation stalls (conventional and turn-around). Gilts with at least one Yorkshire parent tended to be more active and performed more chain manipulating and drinking than gilts with at least one Meishan parent, suggesting that the tendency to develop stereotypies may have a genetic basis. Plasma cortisol level and N:L ratio were lower for gilts with at least one Yorkshire parent compared to gilts with at least one Meishan parent, perhaps reflecting differences in coping strategy with regard to stress. Providing more freedom of movement by the use of a turn-around stall neither affected physiological variables thought to measure chronic stress, nor reduced the performance of repetitive behaviors.The role of hunger in the development of stereotypies was investigated in a second experiment. Artificially reducing hunger in gilts by infusing a cholecystokinin octapeptide solution in the post-feeding period reduced feeding motivation measured by operant conditioning. However, the same treatment applied to sows in the post-feeding period decreased activity level, but did not affect the performance of repetitive behaviors.A last experiment was designed to evaluate, on a long-term basis, the relative role of two consequences of food restriction (hunger and lack of foraging substrate) in the development of stereotypies. Feeding sows a high-energy diet without increasing meal size caused behavioral changes indicative of satiety, reduced the performance of chain manipulation and vacuum chewing in the post-feeding period, and prevented the development of stereotypies. On the other hand, providing more opportunity to perform foraging behaviors while maintaining sows on a conventional diet did not consistently affect the performance of repetitive behavior, suggesting that hunger plays a more important role than the lack of foraging substrate in the development of stereotypies. The welfare of pregnant sows may be improved by finding new feeding methods that will satisfy hunger.